This invention has to do generally with quick acting clamping mechanisms for releasably clamping two members firmly together, and with a novel eccentric structure that is useful in such mechanisms and for other purposes.
The invention is especially useful for releasably securing a movable member to a larger, relatively fixed member or base, as for securing a closure member over an aperture to seal a container.
Some aspects of the present invention relate especially to problems that arise when a vessel containing pressurized fluid is opened without first releasing all of its internal pressure. Under that condition the internal pressure may blow the closure wide open, damaging the apparatus or injuring the operator. Accordingly, without implying any necessary limitation, the invention will be described primarily as it relates to securing the closure of such vessels.
Clamp structures of the present invention are typically of the general type including a clamp arm which is pivotally mounted at one end on one of the members to be secured together, and which can be swung about the pivot axis between an idle position or range of positions entirely clear of the other member and a working position or range of positions in which the clamp arm limits relative movement of the two members. When in working position the clamp arm prevents complete separation of the two members, but without necessarily forcibly clamping them together. Actual clamping is obtained in one conventional type of structure, by shifting a hook formation along the clamp arm toward the pivot axis, as by cam or eccentric mechanism. The two members are thereby forced together into firm contact.
For sealing apertures in large pressure vessels such as tank trucks for handling pressurized fluids, for example, the closure member is typically clamped against the outwardly facing aperture rim by a plurality of individually operable clamping mechanisms distributed around the periphery. Improved clamping structures of that general type have been disclosed by the present applicant in his prior U.S. Pat. Nos. 3,269,587, 3,275,187 and 3,292,812. Those patents also describe and claim a variety of safety devices for insuring release of residual pressure from a pressure vessel before the closure member can be fully released. That is typically accomplished in those patented devices by positively blocking the clamp arm from swinging into idle position until after the closure has been lifted free of the aperture rim, which may be done manually or by the pressure itself. Venting action is thereby provided while the clamp arm is still in working angular position where it positively prevents the closure from flying open.